code: def allowed_file(filename):
      return (
          "." in filename
          and filename.rsplit(".", 1)[1].lower() in ALLOWED_EXTENSIONS
      )
  
file_path: OCRmyPDF/misc/webservice.py
imports: from __future__ import annotations
  import os
  import shlex
  from subprocess import run
  from tempfile import TemporaryDirectory
  from flask import Flask, Response, request, send_from_directory
  from werkzeug.utils import secure_filename
label_desc: Use image node_id 1 for calling a global function with example usage: allowed_file(filename) and returns: unknown